Automatic reversing control for electric motors



Jan. 18, 1949.

V.' WEBER AUTOMATIC REVERSING CONTROL FOR ELECTRIC MOTORS 2 Sheets-Sheet1 Filed Aug. e, 1943 f/VI/ENTOQ. l rcroe (Q2552. w 4 4 Jan. 18, 1949. v.WEBER 2,459,350

AUTOMATIC REVERSING GQNTROL FOR ELECTRIC MOTORS Filed Aug. 6, 1943 2Sheets-Sheet 2 INVENTOR l/zc roe (4/25 BEE Patented Jan. 18, 1949AUTOMATIC REVERSING CONTROL FOR ELECTRIC MOTORS Victor Weber,Greensburg, Pa., assignor to Robertshaw-Fulton Controls Company,

tion of Delaware a corpora- Application August 6, 1943 Serial No.497,613

4 Claims. 1

This invention relates to temperature controlling systems and, moreparticularly, to thermostatic controls for shutter or cowl flapactuating mechanisms which regulate the temperature of the coolingsystems of motor driven vehicles, such as aircraft and the like. In mycopending application, Serial No. 489,180, filed May 31, 1943, of whichthe present application is a continuation-in-part, there is disclosedand claimed a control of the type described which includes means forpreventing fluttering of the armature of the relay provided in thecircuit of the reversible electric motor which operates the shutter. Inthe said copending application no provision was made in the system foralternative manual and thermostatic control of the shutter movement andno limit switches were included in the circuit there disclosed. Thisinvention includes such features together with other improvements in thegeneral arrangement of parts as will be apparent hereinafter.

An object of this invention is to control shutter or cowl flap actuatingmechanism by a system of alternative manual or thermostatic means.

Another object of the invention is to combine such forms of control inthe unit so that a defect in one will not affect the proper functioningof the other.

Another object of the invention is to prevent damage from over-runningby providing automatic limit stop means independent of the manual orthermostatic control.

Another object of the invention is to render the device substantiallyunaffected by vibration from outside sources.

Other objects and advantages will become apparent from the followingdescription taken in connection with the accompanying drawings, whereinFig. 1 is aschematic view of the temperature controlling device inconjunction with a wiring diagram of the electrical circuit usedtherewith.

Fig. 2 is a similar schematic view of a modified form; and

Fig. 3 is a side elevation of a detail.

Referring more particularly to the drawing, the reversible electricmotor I operates, through the worm gear l2 and reduction gears l4 andIS, the shaft 18 of the shutter mechanism (not shown). For the purposesof this description it will suffice to state that rotation of the shaft1 8 causes reciprocation of a jack screw 20 to which the shutter or cowlflap mechanism is attached and which is thereby opened or closed toregu-' late the temperature of the cooling system. The

shaft I8 is provided with a pinion 22 which drives a gear 24 attached toa travelling spindle 26 which revolves at a much slower speed than theshaft l8, as will be hereinafter apparent. The travelling spindle 26 islournalled in a bearing 28 which, in the schematic form shown in Fig. 1,is carried on a support 30 for the limit switch mechanism, designatedgenerally by the reference numeral 32. A similar bearing 34 is carriedin alignment with the bearing 28 on the support 30 but is threaded forengagement with a threaded portion 36 formed on the spindle 26.

Positioned in operative relation with the travelling spindle 26 is athermostatic control device, designated generally by the referencenumeral 38. The thermal unit of this mechanism comprises a bulb 40,capillary tubing 42 and expansible diaphragm 44 constituting a fluidtype actuator. The diaphragm 44 is supported in a frame 46 which housesthe thermostatic control mechanism. .The bulb located exterior of theframe 46 is-adapted for immersion in the cooling liquid which circulatesthrough the radiator of the vehicle. Hence, the device operates bychanges in temperature at the bulb 48 causing expansion or contractionof the fluid therein and corresponding expansive or contractive movementof the diaphragm 44. Reference may be had to Fig. 3 for another view ofthis thermostat mech-' anism.

A sub-frame 48 of channel-form cross-section is pivotally mounted at oneend on lugs 50 projecting inwardly of frame 46 and is urged away fromthe adjacent wall of the frame 46 by a leaf spring 52 which is securedat one end to the subframe 48 and has its free end engaging the wall ofthe main frame 46. The leaf spring 52 and sub-frame 48 are suitablyapertured to permit a button 54 carried by the diaphragm 44 to passfreely therethrough into engagement with a thermostat lever 56. Tocounteract the bias of the spring 52 on the sub-frame 48, a calibratingscrew 58 may threadedly engage the frame 48 at the end opposite thepivotal mounting thereof and extend through the wall of the frame 46 forconvenient access from the exterior. An indicator plate 60 is carried onthe frame 46 in operative engagement with the calibrating screw 58 toindicate the extent of adjustment of the frame 48.

The thermostat lever 56 is pivotally mounted between the side walls ofthe channel-shaped subframe 48 andis engaged on one side of its pivotalmounting by the button 54 of the thermal unit. Preferably, the pivotalmounting of I the inwardly ofone side wall of the sub-frame 48-.-

for reciprocation in a direction parallel with the axis of the diaphragmbutton'ili Theroppositeend of the pin 62 engages with a switch placatewhich is pivotally mounted on oppositely disposed cars 68 projectingfrom the sidewalls of the channel-section frame 48. As in the case ofthe thermostat lever 56, the switch blade 66 is pivotally mounted on itsaxis for" obtaining substantial balance therein.

A coil spring 10 is operative between an end wall of the sub-frame48-and. oneend ofalu I2 formed'on the switch blade B6ioneither side ofthe pivotal mounting. Breferably, the. lug. 12- is'symm'etrical aboutthe pivotal mounting ofthe switch.blade 66-. in order to maintainthiselement'in substantial balance asdescribed. The coil spring 10" servesto..b'ias the switch blade 66'- toward the pin 62" whereas expansivemovement ofth'e diaphragm 44communicated through the button 54.to' thethermostat lever. 56. willserve to oppose this bias. The end oftheswitchblade. 66;. beyondthe portion engagedby. the'pin.62,. isinsulatedfiom the otherportion and. carries contacts 14"disposedonopposite: facesnthereof and adapted for engagementl alternately, uponpendulum movement of tlieblade,.with' contacts 1 l6"and"'|8 'carried ona-cQntact-arm-BU. and. suitablyinsulated therefrom..

Thecontacti arm 80"is..interposed. between the switch blade 66v and. thecar. 68 on:- oneside. of" the frame 48 and. may be pivotedonthelatterin. commonwith the switch blade. 66. An abutment' 82" is formed'on the.contactarm.. on theside of its pivotal mounting opposite thecontactsl6''|8. andis biased. for... clockwise movementas viewed in Fig. Lbyacoil spring operas tive between the sub-frame 48. andan-anchora on thecontact arm 80' on the samesideof. the pivotalmounting as the abutment.82. As'in the-- case of the thermostat lever 56 and the switch blade 66,the contact arm 804s preferably-pivota'lly mounted on its axis forobtaining substantial. balance therein.

The abutment 8'2" onv the. contact arm.- 8fl is adapted'to be engagedby,a proiectingportion.

BSof the travellingspindle 26- andisurged into such relation by meansof. the. coil spring. 84. Upon rotation of the gearv 24from the motorI0.. through gearing described. the travelling-spindle 26" will revolveand, .due to .the. threaded. engage-- mentof the portion 36thereonwiththe threaded. bearing. 34, will; reciprocate transversely. ofthe shaft l8"causing pivotal movementofi'the con tact arm 8.0 andconsequent movement. of. the. contacts 16'--'|'8thereon with-respect tothe switch blade contacts.

As previously indicated, in addition. to the structure for operating'theshutter mechanism. automatically according tov the temperature of thecoolingliquid" as sensed by the thermostat bulb 40, this inventioncontemplates independent means for limiting movement. of the shutter.mechanism topreventdamage thereto should ,the thermostat mechanismoverrun; It wilLbe. apparent" that. such independent means..-need only.

operate at'tli'e' extremes of opening and closing movements of theshutter mechanism and that at intermediate positions the thermostatoperation can safely be permitted to control.

Accordingly, as shown in the schematic embodiment of Fig. 1, the spindle26 is provided intermediate the bearings 28 and 3. 5 with a cam elementSBLwhichmay be formed integral with the spindle 26. The cam 88 isadapted to engage alternately with oppositely disposed pins 90-92reciprocably mounted in bearings 94 carried by the frame 301'. The endsof the pins 9i!92 opposite the portion engageable by the cam 88 areadapted to engage with sWitch blades 96-98 whichare biased intoengagement therewith by means-of.c0il springs IEO supported on the frame30. The switch blades 95-458 are pivotally mounted intermediate theirends as at I62 and each: carries a contact lil i at one end and acontact I06 at the other, these contacts being on opposite sides of therespective switch blades. Preferably,..the contact IE6 is insulated fromthe contact I04 'bythe provision of an insulating strip. I08. for theswitch blades 96-8 on the adjacent side of the pivotal mounting M32. Thecontacts 164' engage with fixed contacts H0 mounted. on the frame 30and. the contacts I06 also engage with fixed contacts H2 similarlymounted. Movement of the contacts Hl iand lflfiiiinto. and out ofengagement with the contacts. H211 l2',.respectively, will interrupt therespective.

operating circuits of the motor iii as will be hereinafter described.

Themotor. circuit includes a relay, designated.

generally by reference numeral H 1, and preferably. of. the.double-throw, single-armature type fully described and claimed in mycopending application, SerialNo. 476,395, filed February 19, 1943, nowPatent No. 2,398,681, dated April 16, 19.46. In theschematic form ofthis relay structure shown in Fig.1 the parts may comprise av pair. ofrelaycoils I I6 suitably mounted in spaced relation. on. aframe H3andbetween which a support lzoprojects and forms a pivotal mounting'for.anarmature I22. overlying both coils H6. The armature. I22. carriescontact pairs I24 at opposite ends. thereof .which are adapted to engagewith fixed contact pairs 26 mounted on theirame I I8;

Intheembodiment shown in Fig. 1, electrically operated latching meansare disclosed for maintaining the armature I22 of the relay in eitherof. its attracted positions for a purpose-which will be. apparenthereinafter. To this end, a pair of interrupter switches lZllareprovided and may each comprise a movable contact and a fixed. contact132 which are normally in engagement. The movable contacts. I36 may.conveniently be operated to open contact position by a shaft I34 whichextends between the switches in abuttingrelation therewith and has aprojecting.

end. maintained. inengagement with one end of an operating lever i36bymeans of a coil spring 13'! which biases it to this position. The operatoperator-is. a. maincontrol switch designated generally by,thereference.numeral hit. This main control switch has a switch arm M2movable to three positions, one position designated by the numeral I44being the automatic control position wherein the thermostat can functionto cause opening and closing of the shutter. The remaining twopositions, designated by the numerals I46 and I48, are adapted formanual control instead of thermostatic; in position I46 serving toeffect opening of the shutter mechanism, and in position I48 to causeclosing thereof. Movement of the switch arm I42 to a neutral position,as shown in Fig. 1, serves as the ofi or circuit-breaking position. Theswitch arm I 42 may be connected to a source of current, such as by awire I50 to one terminal of a battery I52, the other terminal of whichis connected to ground.

As the motor I0 is operated alternately in two directions and thecircuit elements described have reverse positions, the electricalcircuit to one winding of the motor may be'a duplicate of that to theother and will be described in this manner. Thus, when the controlswitch I42 is in automatic position I44 the relay coil circuit may betraced from the source of current I52, wire I50, switch I42 in positionI44, wire I54, wire I58 to switch contacts I4 of the thermostatmechanism. Switch contacts I4 may engage either of the contacts IS-18 ofcontact arm 80 and these latter contacts are connected by wires I 60I82to the relay coils II6 respectively. From the relay coils, the wiresI68-I'I0 lead to the fixed contacts II2 of the limit switch 32. WiresI'I2-II4 connect the movable contacts I06, with which contacts II2 areassociated, to ground.

The motor circuit may be traced from common wires I54 and I58 by wiresI64-I68 to the contact pairs I24 of the relay armature with which fixedcontact pairs I26 cooperate. Wires II6I'I8 connect one contact of eachof the pairs I26 with the switch blade contacts I04 of the limit switch32. From contacts III), with which the contacts I04 cooperate, wiresI80I82 connect respectively with the motor windings. The motor isgrounded by wire I84.

The interrupter switches I28 are connected in parallel circuit with therelay coils II6 by wires I88I88, contacts I30I32 and wires I90I82connected to other one contact of each of the pairs I26 of the relay.

The circuit so far described constitutes the operating circuit when theswitch arm I42 is in the automatic position I44. In the manual openposition I46, a wire I92 will connect the source of current I52 with themovable contact I04 of one of the limit switches, while in the closedposition I48 a wire I94 connects the source of current I52 with themovable contact I04 of the other limit switch. As wires I80I82 connectthe fixed contacts I I0 of this switch to the motor I0 it will beapparent that in either of the manual positions the entire automaticmechanism is disconnected from the circuit and the motor is energizedfrom the battery I52 directly through the limit switch mechanism 32only.

In the operation of the device shown in 1, with switch arm I42 inautomatic position I44, it may be assumed that the temperature of theliquid in the cooling system rises and the bulb 4!! which is immersed inthe liquid communicates the temperature rise to the diaphragm 44 causingexpansion thereof. The button 54 thereupon moves the thermostat lever 56on its pivot and the switch arm 66 is thereby moved by the pin 62 intoposition where contacts 14 and T8 engage.

The relay coil circuit described is energized through the right-handrelay coil, as viewed in Fig. 1, and also through the contacts II2, I06at I24-I26, wire I92, interrupter switch contacts I3fi-I32, wire I88,relay coil IIG, wire I10, limit switch contacts Ii2I06 and wire I'M, toground. This latter circuit serves to form a shunt for the relay coilIIB.

Operation of the motor will cause longitudinal movement of thetravelling spindle 2'5 toward the left, as viewed in Fig. 1, to pivotthe contact arm while switch blade 66 maintains contacts ?4--I8 inengagement. However, after the shutter or cowl flap mechanism has beenmoved in an opening direction by operation of the jack screw 20 acertain distance, the spindle 25 will move contact arm 80 on its pivotfar enough in a counterclockwise direction, as viewed in Fig. 1, to openthe contacts I4-18, it being assumed that the diaphragm has ceasedexpanding and switch blade 66 is stationary.

While, under such conditions, the relay coil circuit comprising contacts"-78, wire I62, relay coil IIB, wire I70, limit switch contacts II2-I08and wire I14 to ground, is discontinued by opening of the contactsl'4-!3, the relay armature I22 does not return to its neutral orunattracted position. It will be apparent that the shunt circuit for therelay coil I16, established by relay contacts I24-I26, wire I92,interrupter switch contacts I32I30, wire I88 to relay coil H6 and thenby the described circuit to ground, will serve to maintain the relayaramature in its attracted position. However, after the expiration of atimed period, the cam I38 on shaft IE will operate the bell-crank leverI36 to open the interrupter switch I28 and cause return of the relayarmature I22 to its neutral position.

The gearing between the shaft I8 and travelling spindle 26 is arrangedso that the shutter or cowl flap mechanism is moved between full-openand full-closed positions during the time that spindle 26 makes analmost complete revolution:

The shaft I8, therefore, revolves much faster than spindle 26 andcompletes several revolutions during the period. Accordingly, the camI38 is located on shaft I8 in such relation to the radial position ofthe bell-crank lever E36 which'it operates that after the spindle 26 hastravelled a certain distance the appropriate interrupter switch I28 isoperated.

As it is contemplated that the motor Il) may be energized by directcurrent it will be apparent that the movement of the contact arm 80, asdescribed, to open the contacts 1416, or I4-18, as the case may be, willtend to produce a slight are between these contacts. Such arcing efiectmay be mementarily sufficient to cause retention of the relay armatureI22 in its attracted position and immediately thereafter may beinsuflicient to cause it to retain such position. armature would thenresult but such effect is eliminated by the which maintains the armaturein its attracted position during initial separating movement of the Achattering of the provision of the shunt circuit '4, contacts; I l -'I8-by operation of the thermostat.-

Itrwillbe apparent that the degree of revolutionofsshaft- I 8 before camI38yoperates the interrupter switch constituting the electrical latchingdevice is dependent upon the relative positions of these parts whenshaft rotatiOn begins. However, two or more cams could be provided toreduce the extreme degree of shaft rotation to less than one revolutionbefore the latching devicezis operated. In anygevent, even if thethermostat is satisfied and; further movement of the shutter isnotrequirecl, the completion of the revolution of shaft l 8:to operatethe latch will not cause an increased. movement of the shutter of anyconsequence due to the greater speed of rotation of shaft I8 relative tospindle 26 as described.

It will furthermore be apparent that there, are provided two circuitswhich will maintain the relay in attracted position, one such circuitbeing completedby engagement of contacts 'I I- It;or.I4-,--'I8vofthethermostatic mechanism and the other being the shunt circuitestablished aroundthe relay coil by the interrupter switches I28. Hence,a1- thoughthe relay coil circuit may be energized either when thethermostatic switch contacts I l- I8..or Id-J5 are engaged or when thesecontacts areseparated, it is apparent that the operation ofthe relayarmature I22 to either of its attracted positions must be initiated byclosing of the'thermostatic switch contacts. Thus, after the armaturehas once moved to its attracted position the shuntcircuit of interrupterswitch I28will assume the function of maintaining the attracted positionofjthe relay armature when the thermostat switch contacts open but isitself incapable of causing the-movement to attracted position. If thethermostatic switch contacts are closed when the interrupter switchopens the shunt circuit the shutter willcontlnue its movement as therelay armature remains attracted.

If the temperature at the bulb 40- continuously increases throughout theextent of movement of the: contact arm 80' and switch blade I56, thenthe motor III will continue to run until an almost completerevolution ofthe spindle 26 occurs. Undersuch conditions the cam 88 carried by thespindle 26 will engage with one or the other of the pins 9092, as thecase may be, and cause opening of the limit switch contacts I04-'-I III.Suchmovement of the limit switch contact arms 96 or 98 will also causeopening of the contacts IIIG.I I2. Thus, at the same time as the motorcircuit is deenergized by operation of the limit switch contacts IM-I I0the circuit of the relay coilv I I6 is also deenergized by operation ofthe contacts I06-I I2. The relay armature I22 then returns to neutralposition and is movable to either attracted positions for closing thecircuit to the motor I0 for operation in either direction.

When the liquid in the cooling system to' which the bulb- 40 is exposedbecomes cooler and the diaphragm Micontract's, then the thermostat-lever56 will cause switch arm 661to closecontac-ts 'll I6 of 1 the thermostatmechanism; The circuit through the relay coil and motor IIl'foroperatingthe shutter or cowl'flap mechanism in a closing. direction issimilar to that previously described '1 or the opening direction.Accordingly, as the system will operate inthesame manner whethercontacts 14'I8"or;1'4.16 ofthe thermostat mechanism are closed,furtherclescription is :deemed unnecessary.

As-previously indicated, thecautomatic operation otthe system'may bedispensed with by movement'- of the, main: control switch I 42 toeither; of: the manual. operating positions. I46 or I48: To: open:

the shutter or cowl flap mechanismthacontact arm I42 isengagedwithposition I46 whereas-to effect closing operation the positionI48 is used; In-either position the circuit described from the. sourceof current I52 t the motor I0 includes only the limit switch mechanism32 and the other circuit elements used in connection withthe-automaticposition are dispensed with. Thus, the: danger of a feed-back throughthe system in the event that the relay armature I22 sticks. in attractedposition is eliminated.

A mechanicaldevicefor maintaining the relay armature in attractedposition for a timed period after opening of the thermostatic switchcontacts is disclosed in the embodiment shown inFig. 2. In this systemsimilar reference numerals: have been used to denote parts correspondingto those shown in Fig, 1. Generally, the thermostatic mechanism remainsthe same; the relay structure and limit switches are changed, and theinterrupter, switches are eliminated. In the embodiment of Fig,2,;therefore, a. reversible electric motor: Ill is provided foroperating the shaft I8 throughtthe worm gear I2 and reduction gears I4and 200; the latter-gear. being shown as integral withthe shaft I8. Thegear-200 drivesragearZOZ attached to thetravelling spindle 26which maybein all respects identical with that disclosed in Fig; 1. Thetravelling spindle 26 is journalled in a bearing 28 carried on a support204 for the limit switch mechanism which is designated in thisembodiment'by the reference numeral 206. The threaded-portion of thetravelling spindle ,26, engages: with a threaded bearing 34' carried. onthe support 204 in alignment withbearing 2B and the-projecting end .ofthe spindle engages withthe abutment 82 on contact arm 8|] ofthethermostatic mechanism.

The cam fla'carried on. thetravelling' spindle 26 engages alternatelywith the pins and- 92 to operate the opposed. switch arms 2l'l8-2III of:the limit switch, mechanism. The. switcharm- 208 is pivoted at one endon the support 204- and the opposite end thereof is upturned to engagewith abell-crank lever H2. The bell-crank leven 2I2 is pivotally mountedon the support 2% and has the'end which-engages'the upturned endof theswitch arm 208 also engaging a pin 2I4 reciprocally mounted in thebearing: 28: transversely of the travelling spindle 2.6. The oppositevend of pin Zldprojecting from the bearing 2Bzenages with oneend of thecontact arm 2I0 which is pivotally mounted intermediate its ends on the.support 204. Both contact arms 208 and 2H).

2 are biased into engagement with the pins 90' and 92 by springs Ito.

The-switch arm ZEBcarries a contact 2.I6'betweentheupturned end andtheportion engaged by the pin 90-. Contact'arm 2I0 carries acon tact 218on the end opposite the portion engaged by the pin 2I4-. Contacts 2I6and 2I8 are normally engagedwith fixed contacts 220 mounted on thesupport 2% and are adapted to bedisengagedtherefrom by operation of thepins 90 and 92 by the Cam 83 The opposite end of the bell-crank lever2I2- carries a leverarm 222 pivotally mounted thereon and similarlymounted at its opposite end on an operating lever 224 similar to thelever I36 in the previous embodiment. The operating lever 224 mayalso'be inthe form of abell-crank'hav ing-its oppositeend positioned. tobe engaged by the cam".I39;carried;by thesha-ft I8;

The latching device for the relay in this embodimentmay be similar tothat disclosed'and '9 claimed in my copending application, Serial No.489,180, hereinbefore referred to. Accordingly, a base 226 carries apair of relay coils 228 spaced one from the other and having a support238 projecting therebetween. Pivotally mounted on the support 238 is anarmature 232 carrying contacts 234 on each end thereof. These contactsare adapted to be moved into and out of engagement with fixed contacts236 which are mounted on insulating pads 238 on the base 226, suchmovement being caused by operation of the armature 232 into either ofits attracted positions. One of the insulatin pads 238 is provided witha lug 24!! upon which a latching arm 242 is pivotally mountedintermediate its ends. The latching arm 242 extends into engagingrelation with the armature 232 and is provided with a suitably shapedend for latching engagement therewith when the armature is in attractedposition. The opposite end of the latching arm 242 carries a cross arm244 which pivotally engages with a second latching arm 246 having asimilarly shaped end for engagement with the opposite end of thearmature when in its other attracted position. The latching arm 246 isengaged by an operating bar 248 reciprocally mounted on the base 226 andprojecting therefrom into engagement with the operating lever 224. Acoil spring 250 mounted between the latching arm 246 and the base 226serves to bias the arm into engagement with the operating bar 248.

The circuit arrangement for this embodiment of the invention maycomprise a source of current I52, with wire I50 leading therefrom to themain control switch arm I42. In the automatic position I44 the circuitmay be traced by way of Wires I54I55 to the switch contacts 14 of thethermostat mechanism. The contacts 16-18 of contact arm 88 with whichcontacts I4 cooperate are connected by wires ISO-I62 to the pair ofrelay coils 228, respectively. The relay coils are grounded by the wires256-458, thus completing the relay coil circuit.

The motor circuit in this embodiment includes common wires I 54I58 andwires I64I66 to the relay contacts 234 of the relay armature 232. Wires26Il262 connect the fixed contacts 236 of the relay to contacts 2I6 and2I8, respectively, of the limit switch mechanism. Contacts 220 of thelimit switch with which contacts 2I6-2I8 cooperate are connected bywires 264266 to the motor windings. The motor is grounded by the wireI84 as in the previous embodiment.

In the operation of the mechanical form of latching device for the relaydescribed in connection with Fig. 2, it is apparent that the shaft I8which completes several revolution for every revolution of thetravelling spindle 26 will operate the latchin device through the mediumof the levers described. Thus, assuming that the thermostatic switchmechanism has operated through the circuit described and caused therelay armature 232 to be attracted, then the latch- 'ing arm 242 or 246,as the case may be, will have moved into position to retain the armaturein such attracted position. As the cam I39 carried by shaft I8 movesinto engagement with the bell-crank lever 224 upon every revolution ofthe shaft I8, the latching device will be released for an'instant. Iithen the thermostatic switch mechanism is in the open contact positionand the circuit through the relay coil is deenergized, the relayarmature 232 will return to its neutral position. If, however, thethermostatic switch mechanism is in closed contact position, then 10 theoperation of the latching mechanism by the cam I39 will not affect theposition of the armature which remains attracted.

Since the limit switches 206 in this embodiment are controlling themotor circuit it is essential that the latching device for the relay bereleased whenever the limit switches operate to open the circuit. In theabsence of such provision it will be apparent that the relay armaturewould remain locked in attracted position, although the shutter or cowlflap mechanism had reached the extreme of movement, either closed oropen, and the motor was deenergized. As the next movement of the shuttermechanism would have to be in the opposite direction by reversed motoroperation, the relay armature would necessarily have to reverse itsposition before the circuit for such operation of the motor could occur.Hence, provision is made in this invention for interconnecting the limitswitch mechanism with the latchin device for the relay.

To this end, when the pin 90, for example, is operated by the cam 88 toopen contacts 2I6 228, then the upturned end of the contact arm 208 willcause the bell-crank lever 2I2 to pivot and move the lever 224 throughthe connecting lever 222. When the lever 224 is moved, as described, theeflect is similar to movement of this lever by the cam I39 and thelatching device is released. In a similar manner operation of the pin 92by the cam 88 to open contacts 2I8-220, will cause the end of thepivoted contact arm 2 II) to move the bell-crank lever 2 I 2 through themedium of the pin 2I4. This movement of the bell-crank lever 2 I2 willcause the above described movement of the latching device as will beapparent. The armature immediately returns to neutral position ready tobe moved to attracted position.

As in the previously described embodiment, the manual positions I46 andI48 are so connected with the motor I0 that the circuit includes onlythe limit switch mechanism 206. Accordingly, wire I92 connects positionI46 with limit switch contacts 2I8220 and wire 266 completes the circuitfrom these contacts to the motor I0. In position I48, wire I94, switchcontacts 2I6220 and wire 264 serve a similar purpose. Thus, in thisembodiment also there is no danger of feedback through the system if therelay armature 232 becomes fixed in an attracted position.

The invention includes means for eliminating to a considerable extentthe eifect of vibration of the aircraft or other vehicle on which thesystem is installed which might have deleterious effects on theoperation of the thermostatic mechanism. The thermostat lever 56, switcharm 66 and contact arm 88 are all in substantial balance as describedand, accordingly, the operation thereof should be unaffected by theconditions under which the device is used.

It will be understood that various changes may be made in thearrangement and combination of parts and that the schematic embodimentis subject to various modifications in form within the scope of theappended claims without departing from the spirit of the invention.

I claim:

1. A control system for cowl flap or shutter actuators, comprisingdriving means for the actuator, a control device movable betweenpositions for starting and stopping said driving means actuating meansfor said control device and being operable to stop said driving means,thermally responsive means for operating actacsc 11 said control devicebetween said positions to start said driving means, ansauxiliary controldevice operable in responseto movements of the first said device fromone position to another, :leans' responsive tooperation of saidauxiliary device for maintaining said driving means in driving operationirrespective of subsequent movement of said control device bysaidactuating means from said one position to another to stop saiddriving means, means operated from said driving means and cooperablewith said control device for rendering said maintaining meansineffective after a predetermined period but being adapted to cause saiddriving means to stop only when said control device is in position tostop said driving means, and a position limit control operable from saiddriving means for stopping operation of said driving means andconcurrently causing another operation of said auxiliary control deviceto render said maintainingmeans ineffeotive independently of saidcontrol device.

2. A control system comprising rotatable driving means, a relay having acoil and an armature operable thereby between open and closed positionsrelative to a plurality of relay contacts, a

source of electrical energy, a control device having a plurality ofpivotally mounted .contacts operable between open and closed positions,means responsive to variations in a variable condition for causing saidcontrol device tooperate said pivotally mounted contacts to closedposition, actuating means adapted to be driven-from said driving meansand being operatively associated with said control device for causingthe same to operate said pivotally mounted contacts from closed to openposition, a firstcircuit including said source and said coil andcontrolled by-operation of said pivotally mounted contacts, a secondcircuit including said source and said driving means and controlledbyoperation of said armature relative to a pair of said relay contacts,a shunt circuit for said control device established by operation of saidarmature relative to one of said pair of relay contacts andanother oneofsaid relay contacts, said shunt circuit being adapted to continue.saidsecond circuit-irrespective of the subsequent discontinuance ofsaid first circuit by operation of-said pivotally mounted contacts, andinterrupter. switch means operated intermittently from said drivingmeans and located in said shunt circuit for opening the same after apredetermined period, said interrupter switch means being cooperablewithsaid control device for causing operation of said armature to opensaid relay contacts but only when said pivotally mounted contacts are inopen position.

3. A control system comprising an electric motor, a control circuit forsaid motor including switching means movable between-positions forcontrolling said circuit, electromagnetic means for operating saidswitching means, an energizing circuit for said electromagnetic meansincluding a control device operable for controlling said energizingcircuit, thermally responsive meansfor causing operation of said controldevice formovement of: said switching means to oneiofz said 'positions,actuating means adapted .to be positioned by said motor forcausingoperation of said control device for effecting movement of'said-switching means Ito another said positiony'a holding circuit forsaid electromagnetic :means established upon operation of said switchingmeans to said one position,'and interrupter switch means included insaid holding circuit and adaptedLtG-be positioned by saidmotorior-discontinuingsaid holding circuit aftera predeterminedperiod of saidmotor operation, said interrupter switch means being cooperable withsaid control device for e'ii-ecting movement of said switchingmeans tosaid other position but only whensaid actuating means is in saidposition.

'4. A control system comprising an electric motor, a control circuit forsaid motor including "switching means movable between 'positions forcontrolling said circuit, electromagnetic means for operating saidswitching means, an energizing circuit for said electromagnetic meansincluding a control device operable for'controlling said energizingcircuit, thermally responsive means for causing operation .of saidcontrol devicefor movement of said switching means tonne of'saidpositions, actuating means adapted to be positioned by said'motor forcausing Operation of said control device for effecting movementofsaidswitching means to another said, position, aholding circuit for saidelectromagnetic means established upon operation of said switching means-to said one position, interrupter switch means.included in said holdingcircuit and adapted to'be positioned .by .said motor for discontinuingsaid holding circuit after apredetermined period .of said motoroperation, said interrupter switch means being .cooperable with: saidcontroldevice for effecting movement of said switchingmeans to. saidother position but only when. said actuating means is-in said position,andapositionlimit switch means included in both said control circuit andsaid energizing circuit and-adapted to be positioned byisaid motoriorconcurrentlydiscontinuing the last said circuits independentlyof saidcontrol device.

VICTOR WEBER.

REFERENCES CITED The following references are of record in-the file ofthis patent:

UNITED STATES PATENTS Number Name Date 862,212 Guion :May--3, 1887435,893 Johnson :Sept. 2, 1890 995,036 Shepherd June 13,1911

1,835,907 Shil-and Dec. 8, 1931 2,077,086 Adair Apr. 13, 1937 2,250,437Persons July 22,. 1941 2,277,560 Raney ..Mar. 24, .1942

2,296,374 Weber Sept.;22, l942 2,314,937 "Hannon .Mar. 30, .19432,354,364 Chapman .July .25, 1944

